Transistors have been continuously scaled down in size to increase performance and reduce power consumption. This has led to the advent of more efficient, scalable electronic devices and increased user experiences. However, as transistors have decreased in size, the complexity of manufacturing them for optimal performance has increased. One area of challenge faced by manufactures of high-voltage transistors is managing breakdown voltage (Vbr). Breakdown is the voltage at which the device is switch-off. The gate at 0V and drain will be at a high bias. Vbr is the highest voltage that the drain voltage can sustain before breakdown (e.g. impact-ionization). Controlling Vbr enables manufactures to tailor the transistor to specific switching applications, but is limited by the amount of resistance within the current flow path of the transistor. There is a tradeoff between high Vbr in the off-state and low resistance in the on-state of the transistor.
One approach for addressing this issue is the use of field plates, small structures that extend the gate of a transistor to increase Vbr. Field plates widen the effective depletion width of the transistor, enabling current to flow less restrictively from a source of the transistor to a drain due to an applied gate voltage stimuli. Unfortunately, the addition of field plates increases the number of process steps required to produce transistors and invariably increases the cost of manufacture.
A need therefore exists for forming field plates on a transistor to improve Vbr with minimal formation steps, and the resulting device.